1. Field of the Invention
The present invention relates to a technique for controlling a communication band between different wireless systems.
2. Description of the Related Art
In the case where a current wireless communication system such as EvDO (1× Evolved Data Only Rev. A), for instance, migrates to a next-generation wireless communication system such as LTE/SAE (Long Term Evolution/System Architecture), for instance, there is a phase where the current wireless communication system and the next-generation wireless communication system coexist in the migration period until the next-generation wireless communication system successfully covers sufficient areas.
During this phase, when a wireless terminal moves into an area where a service according to the next-generation wireless communication system is not provided, a handover is performed from the next-generation wireless communication system, down to the current wireless communication system, thereby enabling a continuous provision of communication service. On this occasion, the wireless terminal is required to execute a new authentication process with the current wireless communication system. If it takes time for this authentication process, causing a temporary interruption in communication, and this may deteriorate a quality of the service.
In order to avoid the situation above, for instance, the document “3GPP TS 23.402 V 8.7.0 (2009-09) “9 Handovers with Optimizations Between E-UTRAN Access and CDMA2000 Access”” (hereinafter, referred to as “Non Patent Document 1”) discloses a technique that the authentication process is preliminarily completed with the system being a target of the handover (hand-down), before the handover is carried out, thereby reducing the time required for the handover. If the preliminary authentication is successful, a base station being a destination of the handover reserves resources within its own station, for the wireless terminal that has been subjected to the preliminary authentication.